The present invention is directed to an implantable medication dosage device having an arrangement for injection of a liquid medication into a living organism, said device comprising a medication track that is formed of a subcutaneous refilling septum connected by a line to a medication reservoir which, in turn, is connected by a second line to a remotely controllable medication dosage pump that has an outlet connected by a line to a catheter and the device further includes a filter arrangement for filtering liquid medication being disposed in the second line.
Specific functions of the components of the medication track of implantable medication dosage devices for liquid medication, particularly pumps, valves and catheters, are sensitive to the contamination of liquid medication, which contamination is in the form of solid particles that can appear in spherical shapes or in fiber-like shapes, as well. As a consequence of a slight displacement volume of such a system per work clock and of the hydraulic pump principle, narrow passages, whose clearances are not more than 10 .mu.m at certain locations will occur in the medication track. Blockage or malfunction of the components and/or leakage of the overall system can, consequently, occur at such locations due to particles of this order of magnitude that are located in the stream of the medication. Over and above this, such particles can lead to an increase in the flow resistance and, thus, influence the pump performance in an inadmissible fashion.
In order to avoid such particle-dependent malfunctions of an implantable dosage means, U.S. Pat. No. 4,486,190, whose disclosure is incorporated by reference, discloses providing a filter arrangement which is inserted in a line between the subcutaneous paracentesis septum and the medication reservoir connected thereto by a hose line. This filter arrangement prevents solid particles present in the medication which is being added to the reservoir from proceeding into the medication reservoir. A filter arranged at this location, in fact, makes it possible to avoid manufacture-caused contaminations in the medication solution itself. Particles that occur in the medication reservoir, for example due to denaturing processes of the filled medication or due to contamination, however, are not removed by such a filter.